Date   : Sat, 29 Oct 2005 13:15:13 +0100
From   : jgh@... (Jonathan Graham Harston)
Subject: Re: Formatting a disk beyond 80 tracks

"A. J. Davis" <mail@...> wrote:
> Has anyone ever done any experiments with formatting a disk beyond 80
> tracks?  I first noticed you could get a few more out of a disk about
> ten years ago with a 5.25" drive on a Sinclair Spectrum (with +D interface).
 
I can usually format 82 tracks on a 3.5" disk, giving a 420K HADFS
disk or two 210K DFS disks. You can create an 82-track ADFS disk,
but ADFS doesn't access anything past track 79 on each side.
 
DFS is a single-sided file system, so will just continue past
track 79.
 
HADFS is specifically written to allow it to accesses tracks 80+.
It accesses the lower numbered tracks sequentially, all of side 0
first, then all of side 1, and then accesses tracks 80+
interleaved.
 
ADFS also access disks sequentially, but it's sector address to
physical address translation has no way of specifying an access to
a track numbered 80+.
 
> I was playing around with J.G. Hartson's disk format program -
> http://www.mdfs.net/Software/BBC/FormDFS.txt - and got some interesting
 
Glad to see it's useful.
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
There are three food groups: brown, green and ice cream.